Technical Brief
Thermoforming KYDEX® Thermoplastic Sheet TB - 116 Intoduction
KYDEX sheet has excellent forming properties, which results in uniform wall thicknesses and crisp detail. KYDEX sheet forms to deep draws with low forces when heated to the upper end of the forming temperature range. Unlike many other thermoforming sheets, KYDEX sheet has unusually high resistance to hot tearing.
General Guidelines
- KYDEX sheet will form differently than other thermoplastic materials. - KYDEX sheet is more consistent than other thermoplastics, resulting in fewer rejects. - KYDEX sheet will give better detail than other thermoplastics. - KYDEX sheet can be vacuum, drape, and pressure formed. These methods result in increased levels of detail.
Forming Guidelines
- Oven temperatures should be set differently than the settings used for ABS or FR-ABS. - Typical heater settings (percentage timers) are 30% – 50% top heaters and 50% - 70% bottom heaters. - The most frequent problem is trying to heat the sheet too quickly, particularly on the primary surface. - Cycle times will vary depending on the oven conditions and grade of KYDEX sheet being formed. - When forming KYDEX sheet, it is better to rely on the sheet appearance during heating than on fixed cycle times. - Forming temperatures – Guidelines: (Sheet should not exceed 204°C (400°F). 165 - 177°C (330 - 350°F) for < 1.50mm (0.060”). 182 - 196°C (360 - 385°F) for 1.50mm to 3.20mm (0.060” to 0.125”). 196 - 204°C (385 - 400°F) for > 3.20mm (0.125”) - Ideally the core sheet temperature should be within 10°F of the surface temperature.
Additional Guidelines
Drying is generally not required except in high humidity conditions. If the material needs to be dried, it should be dried at 68°C (155°F) or about 15° below the products HDT for 16 hours for 3.20mm (0.125”) thickness. Two sided (sandwich) heaters are recommended above 2.00mm (0.080”) nominal thickness.
Sheet Appearance During Heating
As KYDEX sheet is heated, the inherent stresses in the sheet will relax.
• Stage I: The heating is marked by wide undulations and softening • Stage II: The material will start to form small ripples (known as oil canning). • Stage III: The material will start to smooth out and sag (KYDEX sheet will generally sag less than other thermoplastics due to its high melt strength.
• Stage IV: The ripples will have smoothed out indicating that most stresses have been removed. 10 to 30 seconds afterwards the sheet is ready to form.
Technical Brief
Thermoforming KYDEX® Thermoplastic Sheet TB - 116 Sheet Appearance During Heating
If you can NOT achieve Stage IV before the sheet blisters and /or smokes excessively, IT IS BEING HEATED TOO QUICKLY. Cut back on the heat and increase the dwell (cycle) time. Thermolabels or Infrared (IR) pyrometer is ideal for determining sheet surface temperature. You should achieve (but not exceed) proper forming temperature at Stage IV. In summary, the main thing to look for when thermoforming KYDEX sheet, is the uniform sag and lack of rippling. At this point, the KYDEX sheet is ready to form. Design Criteria: • Minimum radius (vacuum forming) is generally equal to the nominal thickness (i.e. 0.71mm (0.028”)) thickness. • Mold Shrinkage for male molds is 0.4% - 0.6% and female molds, 0.5% - 0.7%.
Thermoforming Machine Manufacturers
Brown Machine LLC 330 N Ross Street Beaverton, MI 48612 Tel: +1.989.435.7741 or +1.877.702.4142 Fax: +1.989.435.2821 E-mail:
[email protected] Online: http://www.brown-machine.com
Custom Manufacturing, Inc 330 N Ross Street, P.O. Box 434 Beaverton, MI 48612 Tel: 517.435.7741 Fax: 517.426.4049
Modern Machinery 3031 Guernsy Road, Box 423 Beaverton, MI 48612 Tel: 989.435.9071 or +1.888.649.9839 Fax: 989.435.3940 E-mail:
[email protected] Online: http://www.maodernmachineinc.com
Lamco Machine Tool, Inc 135 Industrial Drive, P.O. Box 2357 Moorehead City, NC 28557-2357 Tel: 252.247.4360 Fax: 252.247.4633 E-mail:
[email protected] Online: http://www.lamcomachine.com
MAAC Machinery Corp 801 Hilltop Drive Itasca, IL 60143 Tel: 800.588.MAAC Fax: 630.285.1506 E-mail:
[email protected] Online: http://www.maacsales.com
Plastimach, Inc 704 Executive Blvd. Valley Cottage, NY 10989 Tel: 800.394.1128 Fax: 914.267.2825 E-mail:
[email protected] Online: http://www.plastimach.com/
Adolf Illig Maschinenbau GmBH Mauerstrasse 100 D-74081 Heilbronn Germany Tel: +49.7131.505.0 Fax: +49.7131.505.303 Online: http://www.illig.de/en/index_en.html
Geiss AG Industriestrße 2 D-96145 Seßlach Germany Tel: +49.9569.92.21.0 Fax: +49.9569.92.21.0 E-mail:
[email protected] Online: http://www.geiss-ttt.com
Because we cannot anticipate or control the many different conditions under which this information and our products may be used, we do not guarantee the applicability of the accuracy of this information or the suitability of our products in any given situation. Users should conduct their own tests to determine the suitability of each product for their particular purposes. Data in the physical property table represents typical values and are to serve only as a guide for engineering design. Results are obtained from specimens under ideal laboratory conditions. Right to change physical properties as a result of technical progress is reserved. THE PRODUCTS DISCUSSED ARE SOLD WITHOUT WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE, EITHER EXPRESSED OR IMPLIED, EXCEPT AS PROVIDED IN OUR STANDARD TERMS AND CONDITIONS OF SALE. Buyer assumes all responsibility for loss or damage arising from the handling and use or our products, whether done in accordance with directions or not. In no event shall the supplier or the manufacturer be liable for incidental or consequential damages. Also, statements concerning the possible use of our products are not intended as recommendations to use our products in the infringement of any patent. Consult local code and regulatory agencies for specific requirements regarding code compliance, transporting, processing, recycling and disposal of our products. Product not intented for use as a heat resistant surface. Texture, product grade and other conditions may cause variations in appearance. This information supersedes all previously published data.
Technical Brief
Troubleshooting Thermoforming Problems TB - 117 Intoduction
The most common problem in thermoforming KYDEX® thermoplastic sheet is one of trying to heat KYDEX sheet too quickly. See the chart below for recommended heating times when sandwich heaters are used. If a problem still exists, review the troubleshooting section of this brief.
Approximate Heating Times
Sheet Thickness
Time (Seconds)
1.00mm (0.040”)
15-35
1.50mm (0.060”)
50-70
2.00mm (0.080”)
65-85
2.40mm (0.093”)
80-100
3.20mm (0.125”)
100-130
4.70mm (0.187”)
180-200
6.40mm (0.250”)
240-285
Heating will vary with the type of heaters being used and the percentages the heaters are set to.
Troubleshooting
Problems
Causes
Remedies
Blister or Bubbles
Heating too Quickly
1) Lower heater(s) temperatures 2) Use slower heating 3) Increase distance between heaters and sheet.
Excessive Moisture
1) Pre-dry material. 2) Heat material from both sides. 3) Lower heater temperatures (more soak time).
Uneven Heating
1) Hot spots (install screening to deflect heat from overheated areas). 2) Check heaters for proper operation. 3) Adjust heater zones to balance sheet surface temperature.
Sheet too Cold
1) Increase dwell time to heat sheet longer. 2) Increase temperature of heaters. 3) Check heaters for proper operation. 4) Pre-heat clamping frame (cold frame can draw heat from sheet). 5) Check for air drafts across sheet ( open doors, fans, etc.).
Insufficient Vacuum
1) Check vacuum holes for blockages. 2) Increase the number of vacuum holes. 3) Increase size of vacuum holes. 4) Check for vacuum leaks.
Poor Detail in Formed Part
Technical Brief
Troubleshooting Thermoforming Problems TB - 117 Troubleshooting
Problems
Causes
Remedies
Poor Detail in Formed Part
Vacuum not drawing Fast Enough
1) Check the vacuum gauge for minimum of in. /Hg pressure. 2) Check for vacuum leaks. 3) Use slots instead of vacuum holes. 4) Increase the size of the vacuum surge tank or vacuum capacity. 5) Check vacuum hose for leaks or collapse.
Poor Detail in Formed Part
Improper pressure
1) Use 20 - 50 psi (.137 - .345 Mpa) air pressure.
Sheet Scorched
Surface of the Sheet too Hot
1) Reduce heating cycle (dwell time). 2) Lower heater temperature (more soak time).
Blushing or Discoloration
Excessive Heat
1) Reduce cycle time (poor detail may occur due to material being too cold). 2) Reduce heater temperatures (increasing dwell time may be required). 3) If problems exist in one area only, check heaters.
Whitening of Part in Corners
Sheet too Cold
1) Increase the dwell time. 2) Reduce platen time delay. 3) reduce vacuum delay.
Webbing, Bridging or Wrinkling
Sheet too Hot
1) Reduce heating time. 2) Lower heater temperatures.
Insufficient Vacuum
1) Check mold for proper vacuum. 2) Check vacuum lines for restrictions.
Excessive Draw Ratio or Poor Mold Design
1) Redesign mold. 2) Increase the draft and radii of the mold design. 3) Use a plug assist. 4) Add take-up blocks (web catchers) to pull material away from the corners. 5) Use recessed pockets (web moats) in web areas. 6) If tooling is multiple mold design, increase the distance between molds.
(when pressure forming)
Technical Brief
Troubleshooting Thermoforming Problems TB - 117 Troubleshooting
Problems
Causes
Remedies
Nipples on Mold Side of Formed Part
Sheet too Hot
1) Reduce dwell time. 2) Reduce heater temperatures.
Vacuum Holes
1) Plug vacuum holes and re-drill with smaller bit.
Excessive Sag After Heating
Sheet too Hot
1) Reduce dwell time. 2) Reduce heater temperatures. 3) Balance sheet surface temperature (increase the perimeter heat and lower center heat).
Chill Marks or "Mark-Off Lines"
Mold Temperature too Cold
1) Increase the mold temperature (do not excess 165ºC) if the mold is water cooled. If the mold is not temperature controlled, pre-heat the mold with a torch. 2) Increase the pre-stretch to allow the mold to come in contact with the material later.
Plug Assist Cold
1) Use a syntactic foam plug assist. 2) Cover plug assist with flannel or felt.
Sheet too Hot
1) Reduce dwell time. 2) Reduce heater temperatures.
Pock Marks on Smooth MoldSurface
1) Air entrapment (sand blast mold texture with #30 shot grit).
Dirt on Sheet or Mold
1) Clean sheet and/or mold surface prior to forming.
Shiny Streaks or Spots
Sheet Overheated in Areas
1) Adjust heaters in affected areas. 2) Hot spots (screen areas to deflect heat, if unable to do with zoning).
Distortion in Part after Removing Part from the Mold
Removing Part From Mold too Soon
1) Increasing the cooling cycle. 2) Use temperature controlled mold. 3) Use fans or water mist.
Uneven Cooling
1) Cool part evenly by adding additional water coolings to mold and/or add fans. 2) Poor Material distribution (improve pre-stretch or plug assist).
Mold Temperature
1) Lower mold temperature 10º below HDT of material.
Surface imperfections
